This is an application for a shared instrumentation grant to obtain a high resolution transmission electron microscope at the Tufts University Schools of Medicine. The Philips CM10 will provide researchers in this community with a contemporary transmission electron microscope uniquely suited for the immunolocalization of specific proteins and subcellular compartments in chemically fixed and or frozen biological materials. A major user group of NIH-funded scientists associated with the Department of Anatomy and Cellular Biology is identified; in addition, a minor user group comprised of scientists from five academic departments and the undergraduate and medical school campuses is recognized that will draw upon this instrumentation for the performance of contemporary techniques in cell biological research that include: (a) immunolocalization of proteins labelled with gold or ferritin, (b) the analysis of fresh frozen thin sections, (c) examination of rotary shadowed and deep-etched specimens, (d) morphometry, (e) examination of thick specimens (both sections and whole mounts) and (f) negative stain preparations. The requested instrumentation will benefit the growing needs of a diverse group of biomedical scientists whose research programs depend heavily on the availability of a high-resolution transmission electron microscopy.